Everolimus therapy in a patient with tuberous sclerosis and a mutation in the LRP5 gene

Tuberous sclerosis complex is a genetic condition that causes the body to grow benign, non-cancerous tumors in various organs. These growths, known as hamartomas, can appear in the brain, skin, heart, lungs, and kidneys. The condition arises when a specific set of instructions in a person's DNA goes wrong, leading to a signaling pathway inside cells that runs out of control. This pathway, which normally helps regulate cell growth, becomes overactive, causing cells to multiply too quickly and form these abnormal masses. While the disease affects many parts of the body, the kidneys are often a primary concern. In most cases, the kidneys develop fatty tumors called angiomyolipomas, but sometimes they develop fluid-filled sacs known as cysts. Doctors have learned to use a class of drugs that can calm this overactive signaling pathway, potentially preserving renal function and managing the growth of these tumors. One such drug, everolimus, has become an important therapeutic option for managing the kidney complications of this condition, offering hope that the disease can be kept in check, particularly when initiated early.

A team of researchers from the University of Novi Sad Medical Faculty recently shared the story of a young patient whose experience with this disease did not follow the expected script. The child was diagnosed with tuberous sclerosis complex at seven months of age after experiencing episodes of staring and limb twitching. Medical scans revealed the classic signs of the condition in the brain and on the skin, but the kidneys presented a unique puzzle. Instead of the more common fatty tumors, the child's kidneys were enlarged and filled with numerous cysts. When genetic testing was performed, the doctors found no errors in the two genes, TSC1 and TSC2, that are typically responsible for the disease. Instead, they discovered a single variation in a different gene called LRP5. This gene is usually associated with bone and eye health, and its connection to kidney cysts is rare and not well understood.

Driven by the hope that calming the overactive cellular pathway would help, the medical team began treating the child with everolimus at four years of age. This decision was made despite the absence of the typical fatty tumors, based on the belief that the drug might still slow the growth of the cysts. For three and a half years, the child was monitored closely. The results, however, were unexpected. While the child's kidney function remained healthy and stable, the cysts did not stop growing. Over the course of the treatment, the kidneys continued to enlarge, and the cysts inside them grew larger and more numerous. The drug appeared to have no effect on the progression of the cystic disease, a stark contrast to other cases where the same medication has led to a marked reduction or complete disappearance of renal cysts.

This case is significant because it is the first time a patient with tuberous sclerosis complex and a variation in the LRP5 gene has been reported. The researchers observed that the child's kidneys kept growing despite the therapy, suggesting that the LRP5 variation might be influencing how the disease manifests in the kidneys. It is possible that this specific genetic difference makes the cysts resistant to the drug, or that the timing of the treatment was not optimal, though the authors cannot say for certain. They note that in other reported cases without this specific gene variation, everolimus has led to a marked reduction in cyst size. Here, the drug failed to halt the progression, even though the patient's overall health remained good.

The study concludes that while everolimus is a powerful tool for many patients with this condition, it may not work for everyone, particularly when other genetic factors are involved. The researchers emphasize that the role of the LRP5 gene in this context remains unclear. It could be a random finding, or it could be a key piece of the puzzle that explains why some patients develop severe cystic kidney disease that does not respond to standard treatment. Until more is known, this case serves as a reminder that genetic conditions are complex, and the presence of a single variation can change the course of the disease in ways that current therapies cannot yet predict or control.